1. Field of the Invention
This invention relates to a process for preparing cyclized polymers of conjugated hydrocarbon dienes. More particularly it relates to the polymerization of such dienes in the presence of a catalyst system comprising a cobalt or nickel component, a hydrocarbyl aluminum and a halogenated hydrocarbon such as CCl.sub.4, CHCl.sub.3, CH.sub.2 Cl.sub.2, etc.
2. Related Prior Art
A pertinent reference relating to cyclized polymers of conjugated dienes is the article by M. A. Golub entitled "Thermal Rearrangements of Unsaturated Polymers" which appeared in Vol. 51 of "Rubber Chemistry and Technology", pages 677-685. However the disclosures therein pertain to preformed polymers having unsaturated side chains which are post-reacted thermally to form cyclic structures. There is no disclosure of cyclic structures formed during or immediately upon polymerization.
A number of patents disclose anionic catalyst systems somewhat resembling those used in the present invention. However, none of these show the production of cyclized polymers from monomeric conjugated dienes.
For example, U.S. Pat. No. 3,084,144 describes the polymerization of fluorine-containing polymerizable compounds using titanium tetrachloride with aluminum alkyl compounds, including trialkyl aluminum together with a chlorine-containing compound such as CCl.sub.4, CH.sub.2 Cl.sub.2, etc. While reference is made to the use of other halides, including those of cobalt in place of the titanium tetrachloride, there is no teaching or indication of the formation of cyclic polymer products.
U.S. Pat. Nos. 3,476,830 and 3,489,823 are concerned with the production of block copolymers of butadiene. In discussing the solvents that may be used in the polymerization, reference is made to "indifferent liquids" and after listing a number of aliphatic and aromatic hydrocarbons patentee adds "and halogenated derivatives of these hydrocarbons such as chloroform, bromobenzene and methylene chloride . . . ". However no reference is made to the production of cyclized polymers nor is there any reference to the fact that the polymerization with halogenated hydrocarbons produces products any different from those produced with hydrocarbon solvents.